| Park | Scotland | Wigtown | All | 1400 - 1700 | 2968 | 342 | ||
| Paterson | Scotland | Ayrshire | Kilmarnock | Kilmarnock | 1750 - 1850 | 7464 | 1168 | |
| Paterson | Scotland | Ross & Cromarty | Foderty | 1850 - 1860 | 7464 | 1172 | ||
| Paterson | Scotland | Midlothian | Edinburgh | 1850 - 1880 | 7464 | 1171 | ||
| Paton | Scotland | Ayr | Galston | -1834 | 5406 | 870 | ||
| Paton | Scotland | Lanarkshire | Hamilton | 1800 - 1899 | 1658 | 1310 | ||
| Paul | Scotland | Aberdeen | Old Machar | 1675 + | 9549 | 820 | ||
| Peace | Scotland | Orkney | Eday / Stronsay | Pre 1855 | 12003 | 1116 | ||
| Pedlow | Ireland | Armagh | Liscorran | Shankill | Lurgan | pre 1740 | 4889 | 907 |
| Pedlow | Ireland | Armagh | Lurgan | Shankill | Lurgan | -1780 | 4889 | 622 |
| Pedlow | Ireland | Armagh | Ballylisk | Kilmore | Ballylisk | -1780 | 4889 | 624 |
| Petrie | Scotland | Fife | Auchtermachy | 1750 + | 11978 | 1139 | ||
| Petrie | Scotland | Fife | 1700 - | 11978 | 1302 | |||
| Phelan | Ireland | Kilkenny | Kilkenny | St John's Well | 1840 - 1870 | 12602 | 1250 | |
| Pickett | Ireland | KIldare | -1840 | 3935 | 369 | |||
| Pierce | Ireland | Offaly | Naas | 1800 - 1860 | 3935 | 885 | ||
| Pierce | Ireland | Kildare | Naas | 1800 - 1860 | 3935 | 368 | ||
| Pigot | Ireland | Kildare | -1840 | 3935 | 370 | |||
| Pittendriech | Scotland | Banff | Inverkeithny | 1820 - 1841 | 8686 | 799 | ||
| Pittendriech | Scotland | Banff | Inverkeithny | 1820 - 1841 | 8686 | 766 | ||
| Pittendriech | Scotland | Aberdeen | Auchterless | Upper Mill | 1810 - 1830 | 8686 | 803 | |
| Porter | Ireland | Down | Seapatrick | Banbridge | 1858 - 1890 | 6873 | 25 | |
| Pratt | Ireland | Laois / Queens | Clonmore | Rathdowney | Errill | 1770 - | 6824 | 1152 |
| Pritchard | Scotland | Lanarkshire | Monkland | 1800 - 1899 | 1658 | 780 | ||
| Ramsay | Scotland | Ayrshire | Kirkoswald | pre 1851 | 5406 | 698 | ||
| Ramsey | Scotland | Ayr | Kirkoswald | -1805 | 5406 | 864 | ||
| Rankin | Scotland | Lanarkshire | 1800 - 1899 | 1658 | 1311 | |||
| Reid | Scotland | Fife | Scoonie | Leven | 1800 - 1855 | 7045 | 1263 | |
| Reid | Scotland | Renfrew | Paisley | 1800 - 1834 | 6058 | 1276 | ||
| Reid | Scotland | Mid-Lothian | St Cuthberts | Edinburgh | 1760 - 1850 | 7045 | 1356 | |
| Reid | Ireland | Tipperary | 1834 - 1836 | 6058 | 1275 | |||
| Reidy | Ireland | Clare | Kilfarboy | Milltown | 1810 - 1890 | 3416 | 326 | |
| Ringwood | Ireland | Wicklow | Ballynure | 1700 - 1900 | 9321 | 1002 | ||
| Robertson | Scotland | Fife | Leslie | Prinlaws Village | 1800 - 1850 | 3818 | 1206 | |
| Roche | Ireland | Tipperary | Kiltankin | 1780 + | 11978 | 1132 | ||
| Roger / Rodger | Scotland | Fife | Strathmiglo | 1780 - 1850 | 9165 | 1202 | ||
| Rogers | Ireland | Meath | 1800 - 1840 | 7045 | 1258 | |||
| Rosie | Scotland | Orkney Is. | Flotta | 1700 - | 7087 | 1307 | ||
| Ross | Scotland | Ross & Cromarty | Foderty | 1800 - 1860 | 7464 | 1173 | ||
| Rowan | Ireland | Kilkenny | Kilkenny | St John's | Kilkenny | 1600 - 1800 | 2968 | 336 |
| Rue | Scotland | Lanarkshire | Glasgow | 1600 - 1788 | 2968 | 356 | ||
| Ryan | Ireland | 1700 + | 11978 | 1137 | ||||
| Saunders | Scotland | Dumfrieshire | Annan | 1800 - 1899 | 1658 | 901 | ||
| Scott | Scotland | Perthshire | Perth | 1724 | 3487 | 894 | ||
| Scott | Ireland | Down | Ballinran | Kilkeel | 1800 - 1898 | 1658 | 197 | |
| Scott | Scotland | Angus | Montrose / Dundee | 1790 - | 13410 | 1322 | ||
| Seater | Scotland | Orkney | Eday / Stronsay | Pre 1880 | 12003 | 1195 | ||
| Seater | Scotland | Orkney | Westray | Pre 1880 | 12003 | 1117 | ||
| Shannahan | Ireland | Tipperary | 1800 - 1840 | 6058 | 1272 | |||
| Shannon | Ireland | Clare | -1856 | 12358 | 1177 | |||
| Shearer | Ireland | Tyrone | Clonfeacl | Coolkill | 1826 - 1857 | 3416 | 315 | |
| Shearer | Ireland | Tyrone | Clonfeacl | Moy | 1827 | 3416 | 316 | |
| Shearer | Ireland | Tyrone | Clonfeacl | Benburb | 1848-1857 | 3416 | 317 | |
| Shearer | Ireland | Tyrone | Drumragh | Omagh | 1797 | 3416 | 318 | |
| Shearer | Ireland | Tyrone | Coolkill | Clonfeacl | 1790 - 1857 | 3416 | 211 | |
| Shearer | Ireland | Antrim | Carnmoney | 1760 - 1850 | 3416 | 324 | ||
| Shearer | Scotland | Anywhere | -1797 | 3416 | 330 | |||
| Sherar | Ireland | Leitrim | Mohill | Mohill | 2876 | 844 | ||
| Sheridan | Ireland | Wexford | Newtonbarry | 1821 - 1842 | 12349 | 1369 | ||
| Sherriff | Scotland | Aberdeen | Kintore | 1790 + | 10126 | 1096 | ||
| Simpson | Scotland | Wigtown | All | 1400 - 1700 | 2968 | 343 | ||
| Sinclair | Scotland | East Lothian | Prestonkirk | 1791 + | 10126 | 1099 | ||
| Sinclair | Scotland | Aberdeen | 1842 - | 11385 | 1355 | |||
| Smith | Scotland | Orkney | Eday / Stronsay | Pre 1855 | 12003 | 1120 | ||
| Smith / Smyth | Ireland | Cavan | -1864 | 12358 | 1143 | |||
| Spidie | Scotland | Perthshire | Perth | 1697 | 3487 | 896 | ||
| Spier | Scotland | Ayrshire | 1750 - 1800 | 7464 | 1170 | |||
| Star ( R ) | Ireland | Galway | Woodford | -1840 | 6503 | 1325 | ||
| Stedman | Scotland | Fife | 1780 - | 11978 | 1300 | |||
| Steel / Steele | Scotland | Wigtownshire | Pre 1845 | 12003 | 1118 | |||
| Stenhouse | Scotland | Lanarkshire | Barony | Glasgow | 1800 s | 4335 | 8 | |
| Stenhouse | Scotland | Lanarkshire | Barony | Anderston | 1798 | 4335 | 12 | |
| Stenhouse | Scotland | Lanarkshire | Govan | 1800 s | 4335 | 13 | ||
| Stenhouse | Scotland | Stirling | Airth | 1800 s | 4335 | 15 | ||
| Stephenson | Ireland | 4335 | 3 | |||||
| Stormont | Ireland | Bangor | 1860 - 1900 | 10976 | 1291 | |||
| Stormount | Ireland | Bangor | 1860 - 1900 | 10976 | 1292 | |||
| Strong | Ireland | 1700 - | 7087 | 1305 | ||||
| Stuart / Stewart | Scotland | Renfrew | Port Glasgow | 1800 - 1859 | 6058 | 1278 | ||
| Sullivan | Ireland | Galway | 1800 + | 10126 | 1333 | |||
| Sullivan | Ireland | Armagh | 1800 's | 10126 | 1102 | |||
| Supple | Ireland | Limerick | Castle Connell | 1800 + | 11978 | 1134 | ||
| Sutherland | Scotland | Caithness | Latheron | 1800 - 1850 | 10713 | 1212 |